Prince performs during his 'Welcome 2 America' tour at Madison Square Garden on Feb. 7, 2011 in New York City.

A never-before-heard song from Prince's catalog was released on Thursday (Sept. 13). "Why the Butterflies" is the latest track to surface from the late singer's upcoming album of unreleased songs, Piano & A Microphone 1983, which is set to release in full on Sept. 21.

According to Prince's vault, the piano-driven track was recorded in the fall of 1983 at Prince's Kiowa Trail Home Studio in Chanhassen, Minn. as part of a rehearsal session. As it stands, there is no fully finished studio version of the song that exists. It also remains unclear if the song was meant to be included in Purple Rain, which was recorded between Aug. 1983 and March 1984.

The nine-track, 35-minute Piano & A Microphone 1983 features Prince working on early recordings of tracks like "17 Days" and "Purple Rain" from the comfort of his home studio.